1. Field of the Invention
The present invention relates to a mobile communication system, and in particular, to selecting and managing a mobility protocol between a network and a terminal in a mobile communication system.
2. Description of the Background Art
In order to meet a variety of forums and new technologies related to the 4th generation mobile communications, the 3rd Generation Partnership Project (3GPP) which aims to provide technical specifications of the 3rd generation mobile communications system has proceeded with research for the Long Term Evolution/System Architecture Evolution (LTE/SAE) technologies since year-end 2004 as a part of efforts to optimize and enhance performances of the 3GPP technologies. The SAE mainly led by the 3GPP SA WG2 relates to research of network technologies which aims to determine a network structure together with the LTE work of the 3GPP TSG RAN and to support mobility between networks of different versions. Recently, the SAE has been considered one of the essential standardization issues of the 3GPP. Such work is to develop the 3GPP to be a system based on the IP and supporting a variety of radio (wireless) connection technologies, and has progressed with the aim of an optimized packet-based system capable of minimizing a transmission delay with enhanced data transmission capability.
The SAE upper level reference model defined by the 3GPP SA WG2 may include a non-roaming case and roaming cases with a variety of scenarios. Detailed descriptions thereof are given in 3GPP TS 23.401 and TS 23.402. FIG. 1 is a schematic view of such network structure.
One of the distinctive characteristics of the network structure shown in FIG. 1 is that it is based on a 2 tier model having an eNode B of the Evolved UTRAN and a gateway of the core network. The eNode B has a similar function, although not exactly the same, to the eNode B and RNC of the existing UMTS system, and the gateway has a function similar to the SGSN/GGSN of the existing system. Another distinctive characteristic is that different interfaces are exchanged by the control plane and the user plane between the access system and the core network. While an Iu interface exists between the RNC and SGSN in the existing UMTS system, two separate interfaces, i.e., S1-MME and S1-U, are used in the Evolved Packet Core (SAE) system since the Mobility Management Entity (MME) which handles the processing of a control signal is structured to be separated from the gateway (GW).
Next, there are two types of gateways: a Serving Gateway (SG) and a Packet Data Network (PDN) gateway. In general, the serving gateway (SG) may serve as an anchor point for handling mobility management within the 3GPP network, and the PDN gateway may serve as an anchor point for handling mobility management of the 3GPP network and the non-3GPP network. These two gateways, however, may also be implemented with a Single Gateway Configuration Option.
As mentioned above, as the specifications for the non-3GPP interworking are formed, different protocols of the IETF have been introduced, in addition to the GTP protocol that has been traditionally used in the existing 3GPP. In particular, IETF protocols, such as the Proxy Mobile IPv6 (PMIPv6), the Dual Stack Mobile IPv6 (DSMIPv6), etc., have been introduced in its draft version prior to the Request for Comments (RFC) of the IETF, and used as an essential protocol for the non-3GPP interworking in the current SAE specifications. Basically, the GTP protocol is used for 3GPP Inter Radio Access Technology (Inter-RAT) handover, and the IETF-based protocols are used for S2 interfaces for the non-3GPP interworking. In particular, a reference point which provides a user plane tunneling and a tunnel management between the serving gateway and the PDN gateway, a reference point which is used with a reference point S5 in roaming, and a reference point S8 can be used in both the GTP and the IETF-based protocols. The table 1 shows available protocol options for several important reference points in the SAE structure (architecture) as below.
TABLE 1ReferencePointsSectionProtocolS1-UE-UTRAN ← → Serving GWGTP-US3SGSN ← → MMEGTPS4SGSN ← → Serving GatewayGTPS5Serving Gateway ← → PDNGTP, PMIPGatewayS8Inter PLMN variant of S5GTP, PMIP(roaming)S2aTrusted non 3GPP IPPMIPv6, CMIPv4 FA CoAaccess ← → GatewayMode,DSMIPv6S2bePDG ← → GatewayPMIPv6S2cUE ← → GatewayDSMIPv6
The mobility management in the SAE may be roughly divided into two types. One is mobility between the 3GPP Inter-RAT systems, and the other is mobility between the 3GPP access system and the non-3GPP access system.
With recent trends of the network evolution to be evolved into the 4th generation All-IP network, a network structure in which various types of access systems can be connected to the core network is foreseen. However, such various types of access systems may utilize different interfaces (reference points) when they are connected to the network. In addition, options for using different mobility protocols are required within each interface (reference point). If such conditions or options do not exist, a possibility of failure in IP tunnel setup between the terminal and the network would increase. In addition, unnecessary interaction between the terminal and the network occurs greatly, thus to cause the waste of network resources in a wired/wireless interface.